Olefin metathesis catalysts and related methods

ABSTRACT

The present invention provides methods for the synthesis of catalysts and precursors thereof. Methods of the invention may comprise combining a catalyst precursor and at least one ligand to generate a catalytically active species, often under mild conditions and in high yields. In some cases, a wide variety of catalysts may be synthesized from a single catalyst precursor. Methods of the invention may also include the preparation of catalysts which, under reaction conditions known in the art, may have been difficult or impossible to prepare and/or isolate due to, for example, steric crowding at the metal center. The present invention also provides catalyst compositions, and precursors thereof, which may be useful in various chemical reactions including olefin metathesis. In some cases, methods of the invention may reduce the number of synthetic and purification steps required to produce catalysts and/or other reaction products, as well as reducing time, cost, and waste production.

FIELD OF THE INVENTION

The present invention generally relates to compositions useful asorganometallic catalysts, and related methods.

BACKGROUND OF THE INVENTION

Transition metal-catalyzed reactions which form carbon-carbon bonds havebecome an important tool in synthetic organic chemistry. One example istransition metal-catalyzed olefin metathesis, which has been shown to beuseful in the synthesis of high molecular weight polymers,pharmaceuticals, and other materials. Olefin metathesis may be definedconceptually as a mutual exchange of alkylidene units between twoolefins involving both the formation and cleavage of carbon-carbondouble bonds, i.e., via [2+2] cycloadditions between an M=C center and acarbon-carbon double bond. Metal alkylidene complexes includingruthenium and molybdenum alkylidene complexes have been shown to performolefin metathesis in the presence of a variety of functional groups.However, in many cases, multi-step syntheses are required to generatethe catalyst compositions.

In some applications, variation of the substituents and/or ligands ofthe catalyst may greatly affect the performance of the catalyst. Forexample, in asymmetric olefin metathesis, the stereoselectivity of acatalyst may be largely affected by the steric size and/or electronicproperties of, for example, ligands bound to the metal center of thecatalyst. Thus, the availability of a wide variety of catalysts, eachhaving different combinations of ligands and/or substitutents, may beadvantageous in optimizing catalysts and/or reactions conditions for aparticular chemical reaction. However, using methods currently known inthe art, the synthesis and isolation of many different catalystcompositions may be impractical. In some cases, the substitution orreplacement of ligands bound to an organometallic catalyst may occurslowly and/or incompletely, or not all. In other cases, the synthesis oforganometallic catalysts may occur with poor yield due to the occurrenceof side reactions. For example, the syntheses of metal alkylidenecomplexes for olefin metathesis may often result in low yields due tocompetitive side reactions including deprotonation of the alkylidene.

Accordingly, improved methods are needed.

SUMMARY OF THE INVENTION

The present invention relates to compositions of matter comprisingcompounds having the structure,

wherein M is Mo or W; R¹ is alkyl, heteroalkyl, aryl, or heteroaryl,optionally substituted; R² and R³ can be the same or different and arehydrogen, alkyl, heteroalkyl, aryl, or heteroaryl, optionallysubstituted; R⁴ and R⁵ can be the same or different and are heteroalkylor heteroaryl, optionally substituted, or R⁴ and R⁵ are joined togetherto form a bidentate ligand with respect to M, optionally substituted;and wherein R⁴ and R⁵ each comprise at least one nitrogen atom.

The present invention also provides methods for synthesizing a catalystcomprising providing a compound having the structure,

wherein M is Mo or W; R¹ is alkyl, heteroalkyl, aryl, or heteroaryl,optionally substituted; R² and R³ can be the same or different and arehydrogen, alkyl, heteroalkyl, aryl, or heteroaryl, optionallysubstituted; R⁴ and R⁵ can be the same or different and are heteroalkylor heteroaryl, optionally substituted, or R⁴ and R⁵ are joined togetherto form a bidentate ligand with respect to M, optionally substituted;and wherein R⁴ and R⁵ each comprise at least one nitrogen atom; andreacting the compound with an oxygen-containing ligand such that theoxygen-containing ligand replaces R⁴ and R⁵ to form a catalyst.

The present invention also provides methods for forming and using acatalyst comprising providing a catalyst precursor comprising anorganometallic composition including a first nitrogen-containing ligandin a reaction vessel; replacing the first, nitrogen-containing ligandwith a second, oxygen-containing ligand thereby synthesizing thecatalyst, at a temperature of less than 100° C. and with a yield of atleast 50%, in the reaction vessel; and catalyzing a reaction in thereaction vessel with the catalyst, wherein the catalyst is present at aconcentration of less than 100 mM.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the synthesis of a catalyst, according to one embodiment ofthe invention.

FIG. 2 shows the synthesis of a catalyst precursor, according to oneembodiment of the invention.

FIG. 3 shows the reaction of a Lewis acid with a composition of theinvention.

FIG. 4 shows the thermal ellipsoid plot (50% probability level) of thestructure of the dimer,{Mo(NAr)(syn-CHCMe₂Ph)(η⁵-NC₄H₄)(η¹-NC₄H₄)}{Mo(NAr)(syn-CHCMe₂Ph)(η¹-NC₄H₄)₂}.

FIG. 5 shows the variable temperature NMR spectra ofMo(NAr)(CHCMe₂Ph)(NC₄H₄)₂ in toluene-d₈.

DETAILED DESCRIPTION

The present invention generally relates to organometallic compositionsuseful as catalysts and catalyst precursors, and related methods.

In some embodiments, the present invention provides methods for thesynthesis of catalysts and precursors thereof. Methods of the inventionmay comprise combining a catalyst precursor and at least one ligand togenerate a catalytically active species, often under mild conditions andin high yields. In some cases, a wide variety of catalysts may besynthesized from a single catalyst precursor. Methods of the inventionmay also include the preparation of catalysts which, under reactionconditions known in the art, may have been difficult or impossible toprepare and/or isolate due to, for example, steric crowding at the metalcenter. The present invention also provides catalyst compositions, andprecursors thereof, which may be useful in various chemical reactionsincluding olefin metathesis. In some cases, methods of the invention mayreduce the number of synthetic and purification steps required toproduce catalysts and/or other reaction products, as well as reducingtime, cost, and waste production.

The present invention may advantageously provide methods for the rapidsynthesis of a wide range of catalyst compositions, in some cases, inyields greater than 95%. The ability to synthesize catalysts rapidly andin high yields may be useful for the screening of known, as well as new,catalysts to determine the optimal conditions and/or reagents for aparticular chemical reaction. In some cases, a catalyst precursor may beused to generate a large number of catalyst structures in which theligands and/or ligand substitutents are varied. For example, the presentinvention may be utilized in the preparation of organometalliccompositions useful as olefin metathesis catalysts, wherein thecompositions comprise imido, alkoxide, and/or alkylidene ligands. Alibrary of such catalysts having varied imido, alkoxide, and/oralkylidene ligands may be prepared and then appropriately screened tooptimize catalyst performance for a given reaction.

Methods of the invention may also be useful for synthesizing catalyststructures that may be difficult to prepare using known methods. Forexample, olefin metathesis catalysts comprising one or more stericallylarge ligands may be prepared in high yields using the methods describedherein, whereas such catalysts may only be prepared in low yields, ornot at all, due to steric crowding at the metal center using knownmethods. In some cases, the present invention may also provide one-potprocedures involving the formation of a catalyst and subsequent use ofthe catalyst in a chemical reaction. The term “one-pot” reaction isknown in the art and refers to a chemical reaction which can produce aproduct in one step which may otherwise have required a multiple-stepsynthesis. One-pot procedures may eliminate the need for isolation(e.g., purification) of catalysts and/or intermediates, while reducingthe number of synthetic steps and the production of waste materials(e.g., solvents, impurities). This may also be advantageous in caseswhere relatively unstable catalysts may be needed for catalyticpurposes.

Accordingly, in some embodiments, the present invention provides variouscompositions including organometallic compositions useful as catalystprecursors. As used herein, a “catalyst precursor” may refer to achemical species which, upon activation, may produce an active catalystspecies in a reaction. For example, an organometallic composition maycomprise a first ligand which, upon activation, may be replaced with asecond ligand to generate the catalytically active species. Theactivation step may comprise exposure of the catalyst precursor to, forexample, an oxygen-containing ligand or other species. As shown in theillustrative embodiment shown in FIG. 1, a catalyst precursor comprisingtwo pyrrolyl ligands may be activated to form a catalyst comprising abiphenolate ligand. In some cases, a single catalyst precursor may beactivated to generate a wide variety of catalysts, often in high yields.The catalyst precursor may be isolated as a stable compound and, in somecases, may be converted in situ into the active form of the catalyst. Asused herein, the term “catalyst” includes active forms of the catalystparticipating in the reaction. In some embodiments, catalyst precursorsof the invention may be advantageous in that the chemical composition,amount, and/or release of the catalytically active species may becontrolled.

In some cases, the present invention provides catalyst precursorscomprising compounds having the structure,

wherein M is Mo or W; R¹ is alkyl, heteroalkyl, aryl, or heteroaryl,optionally substituted; R² and R³ can be the same or different and arehydrogen, alkyl, heteroalkyl, aryl, or heteroaryl, optionallysubstituted; R⁴ and R⁵ can be the same or different and are heteroalkylor heteroaryl, optionally substituted, or R⁴ and R⁵ are joined togetherto form a bidentate ligand with respect to M, optionally substituted;and wherein R⁴ and R⁵ each comprise at least one nitrogen atom. In somecases, M is Mo.

In some embodiments, R⁴ and R⁵ can be the same or different and areheteroaryl groups comprising at least one nitrogen ring atom. In somecases, R⁴ and R⁵ each coordinate M via a nitrogen atom. For example, R⁴and R⁵ may both be pyrrolyl groups which coordinate the metal via thenitrogen atoms of the pyrrolyl ring. R⁴ and R⁵ may comprise otherheteroaryl or heteroalkyl groups, or R⁴ and R⁵ may be joined to form abidentate ligand, such as a biphenolate or binaphtholate group. In somecases, at least one of R⁴ and R⁵ is a chiral ligand, or R⁴ and R⁵ arejoined together to form a chiral ligand.

In some embodiments, at least one of R² and R³ may be hydrogen, suchthat, when R² is hydrogen, R³ may be alkyl, heteroalkyl, aryl, orheteroaryl, optionally substituted, or, when R³ is hydrogen, R² isalkyl, heteroalkyl, aryl, or heteroaryl, optionally substituted. In someembodiments, M is Mo; R¹ is substituted aryl; R² is alkyl, optionallysubstituted; R³ is hydrogen; R⁴ and R⁵ are heteroaryl, optionallysubstituted, or R⁴ and R⁵ are joined together to form a bidentate ligandwith respect to M, optionally substituted; and wherein R⁴ and R⁵ eachcomprise at least one nitrogen atom.

The catalyst precursors may be synthesized according to various methodsknown in the art. In an illustrative embodiment shown in FIG. 2, thecatalyst precursor may be synthesized by the addition of lithiumpyrrolide to a mixture of Mo(NR)(CHCMe₂R′)-(OTf)₂(dimethoxyethane),wherein R′ is alkyl, heteroalkyl, aryl, heteroaryl, or substitutedderivatives thereof. The reaction may proceed in high yield (e.g, >95%in some cases) with little or substantially no side reactions, such asthe deprotonation of alkylidene to give an alkylidyne. The synthesis ofthe catalyst precursor may be conducted in the presence of variousorganic solvents, including diethyl ether, dichloromethane, and thelike. In one set of embodiments, dimeric dipyrrolyl complexes,{Mo(NR¹)(CHCMe₂R′)(NC₄H₄)₂}₂, can be prepared readily and in good yieldfrom Mo(NR¹)(CHCMe₂R′)(OTf)₂(DME) species.

The present invention also provides methods for generation of catalyst,including homogeneous catalysts and heterogeneous catalysts. In somecases, the catalyst may be generated in situ to catalyze a chemicalreaction, as described more fully below. Methods for synthesizing thecatalyst may comprise providing a catalyst precursor comprising anorganometallic composition including a first nitrogen-containing ligand.The first, nitrogen-containing ligand may be replaced with a second,oxygen-containing ligand, thereby synthesizing the catalyst. As shown bythe illustrative embodiment in Scheme 1, the method may compriseproviding a catalyst precursor as described herein and reacting thecatalyst precursor with an oxygen-containing ligand (e.g., R⁶ and R⁷)such that the oxygen-containing ligand replaces R⁴ and R⁵ to form thecatalyst, wherein R⁴ and R⁵, in protonated or non-protonated form, maybe released. R⁶ and R⁷ may be oxygen-containing ligands or R⁶ and R⁷ maybe joined together to form a bidentate, oxygen-containing ligand. Insome cases, the oxygen-containing ligand may be in a protonated formprior to coordinating the metal center, and may then have sufficientlyionic character (e.g., may be deprotonated) upon coordination to themetal center. Similarly, the nitrogen-containing ligand may be in adeprotonated form when bound to the metal center, and may becomeprotonated upon release from the metal center. For example, R⁴ and R⁵may be pyrrolyl groups coordinating the metal center such that, uponexposure of the catalyst precursor to an oxygen-containing ligand suchas biphenolate, the biphenolate ligand may replace the pyrrolyl groupsto form the catalyst, resulting in the release of two equivalents ofpyrrole. Ligands of the present invention may be described usingnomenclature consistent with their protonated or deprotonated forms,and, in each case, it should be understood that the ligand will adoptthe appropriate form to achieve its function as, for example, either aligand bound to a metal center or an inert species in the reactionmixture. For example, in an illustrative embodiment, the term “pyrrolyl”may be used to describe a deprotonated, anionic pyrrole group which maycoordinate a metal center, while the term “pyrrole” may be used todescribe a neutral pyrrole group which does not coordinate the metalcenter but may be present in solution as an inert species that does notreact with other components in the reaction mixture.

Scheme 1

The synthesis of catalysts having the structure,Mo(NR¹)(CHR²R³)(R⁶)(R⁷), from catalyst precursors having the structure,Mo(NR¹)(CHR²R³)(R⁴)(R⁵), may require that both R⁴ and R⁵ groups, or abidentate ligand formed by joining R⁴ and R⁵, be replaced readily withR⁶ and R⁷, or a bidentate ligand formed by joining R⁶ and R⁷. In somecases, R⁴ and R⁵ may be selected such that, upon release of the R⁴ andR⁵ groups, the released R⁴ and R⁵ groups may not interfere withsubsequent reactions that may involve the catalyst or may not react withany other species in the reaction. In some cases, the R⁴ and R⁵ groupsmay be released in protonated form (e.g., H—R⁴ and H—R⁵, or H₂(R⁴-R⁵))but may be similarly inert to other species or reagents, including thoseinvolved in subsequent reactions.

Those of ordinary skill in the art would be able to select theappropriate nitrogen-containing ligand(s) (e.g., R⁴ and R⁵) suitable foruse in a particular application. For example, a one-pot synthesis may beperformed to generate a catalyst and to carry out a chemical reactionusing the catalyst, wherein, upon in situ generation of the catalyst,the released nitrogen-containing ligand(s) do not react with reagents ofthe chemical reaction and/or other components of the reaction mixture.In one embodiment, an olefin metathesis catalyst may be generated insitu as described herein and subsequently utilized in an metathesisreaction, wherein the nitrogen-containing ligand(s) of the catalystprecursor may be selected such that the released nitrogen-containingligand(s) do not contain carbon-carbon double bonds which may react withthe generated olefin metathesis catalyst.

The oxygen-containing ligand may be a heteroaryl or heteroalkyl groupcomprising at least one oxygen ring atom. In some cases, theoxygen-containing ligand may be a bidentate ligand (e.g., a diolate), asdescribed herein. In some cases, the oxygen-containing ligand may be achiral ligand. In some embodiments, the oxygen-containing ligand may beattached to a surface of a solid support material, such as an inorganicsubstrate, polymer resin, or other solid support, via a covalent or anon-covalent bond (e.g., an ionic bond, a hydrogen bond, a dative bond,Van der Waals interactions, or the like). Thus, replacement of thenitrogen containing ligand(s) with the solid-supported oxygen-containingligand(s) may generate a heterogeneous catalyst. For example, a siliconsubstrate may comprise —SiOH groups covalently bound to the surface ofthe substrate, wherein the —SiOH groups may coordinate the metal centerof the catalyst precursor to form a heterogeneous, surface-boundcatalyst.

Methods of the invention may be advantageous in that, in some cases, acatalyst may be prepared under relatively mild conditions and in highyields. For example, the replacement of the nitrogen-containingligand(s) with oxygen-containing ligand(s) to form the catalyst mayoccur at a temperature of less than 100° C. and with a yield of at least50%. In some cases, the replacement may occur with a yield of at least50%, at least 60%, at least 70%, at least 80%, at least 90%, or, in somecases, at least 95%. In some embodiments, the replacement may occur at atemperature of less than 80° C., less than 60° C., less than 40° C., or,in some cases, less than 25° C. For example, the replacement of thenitrogen-containing ligand(s) with oxygen-containing ligand(s) may occurat room temperature. In some cases, the catalyst may be prepared by arelatively rapid reaction, with conversion of the catalyst precursor tothe catalyst often occurring within 60 minutes or less, 30 minutes orless, or, in some cases, 15 minutes or less.

In some embodiments, the resulting catalyst may have the structure,

wherein M is Mo or W; R¹ is alkyl, heteroalkyl, aryl, or heteroaryl,optionally substituted; R² and R³ can be the same or different and arehydrogen, alkyl, heteroalkyl, aryl, or heteroaryl, optionallysubstituted; R⁶ and R⁷ can be the same or different and are heteroalkylor heteroaryl, optionally substituted, or R⁶ and R⁷ are joined togetherto form a bidentate ligand with respect to M, optionally substituted;and wherein R⁶ and R⁷ each comprise at least one oxygen atom.

In some cases, R⁶ and R⁷ may be joined together to form a chiral,bidentate ligand of at least 80% optical purity and having sufficientrigidity such that a reaction site is of sufficient shape specificity,defined in part by the chiral, bidentate ligand and a M=N—R¹ site, tocause a molecular substrate having a plane of symmetry to react with aM=C center at the reaction site, forming a product that has at least a50% enantiomeric excess of at least one enantiomer present in themixture, the product being free of a plane of symmetry. In someembodiments, the chiral, bidentate ligand may comprise two linked oxygenatoms such that a group of atoms defining the shortest chemical bondpathway between the two oxygen atoms has at least four atoms. Examplesof chiral bidentate ligands include biphenolates and binaphtholates,optionally substituted with alkyl, alkenyl, alkynyl, cycloalkyl,cycloalkenyl, cycloalkynyl, aryl, alkaryl, aralkyl, optionallyinterrupted or terminated by heteroatoms, carbonyl groups, cyano, NO₂,alkoxy, aryloxy, hydroxy, amino, thioalkyl, thioaryl, sulfur-containinggroups, halides, substituted derivatives thereof, and the like. In somecases, the chiral, bidentate ligand may be substituted at positions inproximity of the metal center to impart stereoselectivity to thereactive site of the catalyst.

In some cases, catalysts comprising one or more sterically large ligandsmay be synthesized. For example, at least one of R¹-R³, R⁶, and R⁷ maycontain sterically large groups, such as tert-butyl, isopropyl, phenyl,naphthyl, adamantyl, substituted derivatives thereof, and the like.Sterically large ligands may also include ligands comprisingsubstituents positioned in close proximity to the metal center when theligand is bound to the metal. Methods as described herein may be used tosynthesize catalysts that may otherwise be difficult or impossible toprepare due to the presence of one or more sterically large groups boundto or proximate the metal center, i.e., steric “crowding” around themetal center. For example, catalysts described herein may comprisesterically large groups on the imido, alkoxide, and/or alkylideneligands. In an illustrative embodiment, methods of the invention may beused to synthesize Mo(N-2,6-Br₂-4-MeC₆H₂)(CHCMe₃)[rac-Biphen], whereBiphen is3,3′-di-t-butyl-5,5′,6,6′-tetramethyl-1,1′-biphenyl-2,2′-diolate.

Upon formation of the catalyst in a reaction vessel, a one-pot proceduremay be performed, wherein the catalyst may be generated in situ and maybe subsequently employed in a chemical reaction, in the same reactionvessel. Those of ordinary skill in the art would be able to select theappropriate catalyst in combination with the chemical reaction to beperformed. The ability to, in a single reaction vessel, generate acatalyst in situ and utilize the catalyst in a reaction, may facilitatethe ability to screen a large number of catalysts for a particularreaction. Also, additional purification may be eliminated, which may beuseful in cases where the catalyst structure may be difficult toisolate. In some cases, the reaction may be a carbon-carbon bond formingreaction. In some cases, the reaction may be an olefin metathesisreaction, such as a ring-closing reaction, a ring-opening reaction, or across-metathesis reaction. The catalyst may be present at aconcentration of less than 100 mM, less than 50 mM, or less than 10 mM.

The catalyst may be provided in the reaction mixture in asub-stoichiometric amount (e.g., catalytic amount). In certainembodiments, that amount is in the range of 0.01 to 50 mol % withrespect to the limiting reagent of the chemical reaction, depending uponwhich reagent is in stoichiometric excess. In some embodiments, thecatalyst is present in less than or equal to about 40 mol % relative tothe limiting reagent. In some embodiments, the catalyst is present inless than or equal to about 30 mol % relative to the limiting reagent.In some embodiments, the catalyst is present in less than or equal toabout 20 mol %, about 10 mol %, about 5 mol %, or about 1 mol % relativeto the limiting reagent. In the case where the molecular formula of thecatalyst complex includes more than one metal, the amount of thecatalyst complex used in the reaction may be adjusted accordingly.

The products (e.g., catalysts, catalyst precursors) which may beproduced by methods of the present invention may undergo furtherreaction(s) to afford desired derivatives thereof. Such permissiblederivatization reactions can be carried out in accordance withconventional procedures known in the art. For example, potentialderivatization reactions include metathesis reactions between thealkylidene moiety of the catalyst or catalyst precursor and an olefin,such that R² and R³ are replaced.

As suitable, the catalysts employed in the present invention may involvethe use of metals which can mediate a particular desired chemicalreaction. In general, any transition metal (e.g., having d electrons)may be used to form the catalyst, e.g., a metal selected from one ofGroups 3-12 of the periodic table or from the lanthanide series.However, in some embodiments, the metal may be selected from Groups 3-8,or, in some cases, from Groups 4-7. In some embodiments, the metal maybe selected from Group 6. According to the conventions used herein, theterm “Group 6” refers to the transition metal group comprising chromium,molybdenum, and tungsten. In some cases, the metal is molybdenum ortungsten. It may be expected that these catalysts will perform similarlybecause they are known to undergo similar reactions, such as metathesisreactions. However, the different ligands are thought to modify thecatalyst performance by, for example, modifying reactivity andpreventing undesirable side reactions. In a particular embodiment, thecatalyst comprises molybdenum. Additionally, the present invention mayalso include the formation of heterogeneous catalysts containing formsof these elements.

As used herein, a “nitrogen-containing ligand” (e.g., R⁴ and/or R⁵) maybe any species capable of binding a metal center via a nitrogen atom. Insome cases, the nitrogen atom may be a ring atom of a heteroaryl orheteroalkyl group. In some cases, the nitrogen atom may be a substitutedamine group. It should be understood that, in catalyst precursorsdescribed herein, the nitrogen-containing ligand may have sufficientlyionic character to coordinate a metal center, such as a Mo or W metalcenter. Examples of nitrogen-containing ligands include, but are notlimited to, pyrrolyl, pyrazolyl, pyridinyl, pyrazinyl, pyrimidinyl,imidazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, thiazolyl,isothiazolyl, indolyl, indazolyl, carbazolyl, morpholinyl, piperidinyl,oxazinyl, substituted derivatives thereof, and the like. Thenitrogen-containing ligand may be selected to interact with anoxygen-containing ligand such that the oxygen-containing ligand canreadily replace the nitrogen-containing ligand to generate the catalyst.In cases where the catalyst composition may be generated in situ inorder to carry out a chemical reaction, the first, nitrogen-containingligand may be selected such that, upon replacement by anoxygen-containing ligand, the nitrogen-containing ligands or protonatedversions thereof do not interfere with the chemical reaction. In oneembodiment, R⁴ and R⁵ may be pyrrolyl groups. In some embodiments, thenitrogen-containing ligand may be chiral and may be provided as aracemic mixture or a purified stereoisomer.

In some cases, R⁴ and R⁵ may be joined together to form a bidentateligand which, when bound to the metal center, forms a metallacyclestructure with the metal center. Bidentate ligands may be any specieshaving at least two sites capable of binding a metal center. Forexample, the bidentate ligand may comprise at least two heteroatoms thatcoordinate the metal center, or a heteroatom and an anionic carbon atomthat coordinate the metal center. Examples of bidentate ligands suitablefor use in the invention include, but are not limited to, aryl andheteroaryl groups, linked directly or via alkyl, heteroalkyl, aryl,and/or heteroaryl groups, substituted derivatives thereof, and the like.

As used herein, the term “oxygen-containing ligand” may be used to referto ligands comprising at least one oxygen atom capable of coordinating ametal atom (e.g., R⁶ and/or R⁷). The term “oxygen-containing ligands”may also describe ligand precursors comprising at least one hydroxylgroup, wherein deprotonation of the hydroxyl group results in anegatively charged oxygen atom, which then coordinates a metal atom. Theoxygen-containing ligand may be a heteroaryl or heteroalkyl groupcomprising at least one oxygen ring atom. In some cases, the oxygen atommay be positioned on a substituent of an alkyl, heteroalkyl, aryl, orheteroaryl group. For example, the oxygen-containing ligand may be ahydroxy-substituted aryl group, wherein the hydroxyl group isdeprotonated upon coordination to the metal center. Theoxygen-containing ligand may also be a bidentate ligand, wherein theligand coordinates the metal center via two oxygen atoms (e.g.,“dialkoxide ligand”).

The oxygen-containing ligand may also be attached to a surface of asolid support material, such as an inorganic substrate (e.g., SiO₂,alumina, etc.), polymer resin, or the like, via a covalent or anon-covalent bond. The solid support material may be any materialcapable of forming a bond with catalysts as described herein. In somecases, the solid support material may comprise functional groups (e.g.,SiOH groups) positioned at the surface of the solid support material,wherein the functional groups may form a bond with the catalyst orcatalyst precursor. The bond may be a covalent bond, an ionic bond, ahydrogen bond, a dative bond, or the like. The bond may also compriseVan der Waals interactions. The support material may be selected to havea particular surface area wherein the solid support material may contacta sufficient amount of a reagent (e.g., catalyst, catalyst precursor,other reagents, etc.) to allow interaction between the surfacefunctional groups and the reagent. In some embodiments, the supportmaterial has a high surface area. In some cases, the support materialhas a surface area of at least 50 mm², at least 100 mm², at least 200mm², at least 300 mm², at least 400 mm², or at least 500 mm².

In some cases, the oxygen-containing ligand may be chiral and may beprovided as a racemic mixture or a purified stereoisomer. In someembodiments, the chiral, oxygen-containing ligand may be present in atleast 80% optical purity, i.e., the oxygen-containing ligand samplecontains 90% of one enantiomer and 10% of the other. In someembodiments, the chiral, oxygen-containing ligand may be at least 90%optically pure, at least 95% optically pure, or, in some cases, at least99% optically pure.

In some cases, the catalyst may comprise a bidentate, oxygen-containingligand (e.g., dialkoxide) having sufficient rigidity such that, inconjunction with an M=N—R¹ site, the combination of the bidentate,oxygen-containing ligand and the M=N—R¹ site in part may confer shapespecificity to a reaction site where the catalyst reacts with a reactantsuch as, for example, an olefin. In some embodiments, the shapespecificity, imparted by rigidity of the bidentate, oxygen-containingligand, may be sufficient to allow a mixture of two enantiomericreactants (e.g., olefins) to react with a M=C center of the reactionsite at different rates. That is, the catalyst may be designed to haveshape specificity sufficient to differentiate between enantiomers of areactant by sterically interacting with one enantiomer almostexclusively or exclusively to achieve enantiomeric selectivity, that is,a preference for one enantiomer over the other. Enantiomeric selectivityby kinetic resolution involves reducing the steric interactions in thetransition state of the reaction of the substrate at the catalyst suchthat the transition state involving one enantiomer is of lower energythan the transition state of the other enantiomer. Consequently, theterm shape specificity in the present invention refers to the shape ofan M=C reaction site in the transition state, as formed by thesurrounding ligands, such that upon reaction of the substrate with themetal compound, one enantiomer “fits into” the binding site with lesssteric interaction than the other enantiomer. The transition stateenergy is lower for the enantiomer with a better “fit” or shapespecificity over the other.

In another embodiment, the chiral bidentate, oxygen-containing ligand ofat least 80% optical purity has sufficient rigidity such that a reactionsite is of sufficient shape specificity, defined in part by thebidentate, oxygen-containing ligand and a M=N—R¹ site, to cause amolecular substrate having a plane of symmetry to react with a M=Ccenter at the reaction site forming a catalytic olefin metathesisproduct that is free of a plane of symmetry. The product has at least a50% enantiomeric excess of at least one enantiomer present in themixture. In some cases, the product may have at least a 60%, 70%, 80%,or 90% enantiomeric excess of at least one enantiomer present in themixture. A method to screen for bidentate, oxygen-containing ligandshaving sufficient rigidity for shape specificity purposes involvesobtaining an enantiomeric mixture of a test bidentate, oxygen-containingligand, isolating one enantiomer and measuring a specific rotation. Abidentate, oxygen-containing ligand of sufficient rigidity would providea specific rotation as opposed to reverting back to an enantiomericmixture.

Catalysts and catalyst precursors of the invention may comprisesubstituted imido groups (e.g., N—R¹). Without wishing to be bound bytheory, the imido group may stabilize the organometallic compositionsdescribed herein by providing steric protection and/or reducing thepotential for bimolecular decomposition. In some cases, R¹ may beselected to be sterically large or bulky, including phenyl groups,substituted phenyl groups (e.g., 2,6-disubstituted phenyls,2,4,6-trusubstituted phenyls), polycyclic groups (e.g., adamantyl), orother sterically large groups. In some embodiments, R¹ may be2,6-dialkylphenyl, such as 2,6-diisopropylphenyl. Catalysts and catalystprecursors of the invention may further comprise substituted alkylidenegroups (e.g., CR²R³). The alkylidene groups may be mono-substituted(e.g., one of R² and R³ is hydrogen) or di-substituted with, forexample, alkyl, heteroalkyl, aryl, or heteroaryl groups, optionallysubstituted. In some cases, the alkylidene may be mono-substituted with,for example, t-butyl, dimethylphenyl, or the like.

The combination of imido, alkoxide, and/or alkylidene ligands may beselected to suit a particular application. For example, in some cases,sterically large or sterically bulky ligands and/or ligand substituentsmay impart a higher degree of stability to a catalyst, while, in somecases, lowering the reactivity of the catalyst. In some cases, smallerligands and/or substituents may generate more reactive catalysts thatmay have decreased stability. Those of ordinary skill in the art wouldbe able to balance such factors and select the appropriate combinationof ligands for catalysts of the invention.

Solvents which may be used in methods of the invention include, but arenot limited to, benzene, p-cresol, toluene, xylene, diethyl ether,glycol, diethyl ether, petroleum ether, hexane, cyclohexane, pentane,methylene chloride, chloroform, carbon tetrachloride, dioxane,tetrahydrofuran (THF), dimethyl sulfoxide, dimethylformamide,hexamethyl-phosphoric triamide, ethyl acetate, pyridine, triethylamine,picoline, mixtures thereof, or the like. In some embodiments, thesolvent may be diethyl ether or dichloromethane.

As used herein, the term “reacting” refers to the forming of a bondbetween two or more components to produce a stable, isolable compound.For example, a first component and a second component may react to formone reaction product comprising the first component and the secondcomponent joined by a covalent bond. That is, the term “reacting” doesnot refer to the interaction of solvents, catalysts, bases, ligands, orother materials which may serve to promote the occurrence of thereaction with the component(s).

The term “organometallic” is given its ordinary meaning in the art andrefers to compositions comprising at least one metal atom bound to oneor more than one organic ligand.

As used herein, the term “alkyl” is given its ordinary meaning in theart and may include saturated aliphatic groups, including straight-chainalkyl groups, branched-chain alkyl groups, cycloalkyl (alicyclic)groups, alkyl substituted cycloalkyl groups, and cycloalkyl substitutedalkyl groups. In certain embodiments, a straight chain or branched chainalkyl has about 30 or fewer carbon atoms in its backbone (e.g., C₁-C₃₀for straight chain, C₃-C₃₀ for branched chain), and alternatively, about20 or fewer. Likewise, cycloalkyls have from about 3 to about 10 carbonatoms in their ring structure, and alternatively about 5, 6 or 7 carbonsin the ring structure.

The term “heteroalkyl” is given its ordinary meaning in the art andrefers to alkyl groups as described herein in which one or more atoms isa heteroatom (e.g., oxygen, nitrogen, sulfur, and the like).

The term “aryl” is given its ordinary meaning in the art and refers tosingle-ring aromatic groups such as, for example, 5-, 6- and 7-memberedsingle-ring aromatic groups.

The term “heteroaryl” is given its ordinary meaning in the art andrefers to aryl groups as described herein in which one or more atoms isa heteroatom (e.g., oxygen, nitrogen, sulfur, and the like). Examples ofaryl and heteroaryl groups include, but are not limited to, phenyl,pyrrolyl, furanyl, thiophenyl, imidazolyl, oxazolyl, thiazolyl,triazolyl, pyrazolyl, pyridinyl, pyrazinyl, pyridazinyl and pyrimidinyl,and the like. It should be understood that, when aryl and heteroarylgroups are used as ligands coordinating a metal center, the aryl andheteroaryl groups may have sufficient ionic character to coordinate themetal center. For example, when a heteroaryl group such as pyrrole isused as a nitrogen-containing ligand, as described herein, it should beunderstood that the pyrrole group has sufficient ionic character (e.g.,is sufficiently deprotonated to define a pyrrolyl) to coordinate themetal center. In some cases, the aryl or heteroaryl group may compriseat least on functional group that has sufficient ionic character tocoordinate the metal center, such as a biphenolate group, for example.

As used herein, the term “substituted” is contemplated to include allpermissible substituents of organic compounds, “permissible” being inthe context of the chemical rules of valence known to those of ordinaryskill in the art. In some cases, “substituted” may generally refer toreplacement of a hydrogen with a substituent as described herein.However, “substituted,” as used herein, does not encompass replacementand/or alteration of a key functional group by which a molecule isidentified, e.g., such that the “substituted” functional group becomes,through substitution, a different functional group. For example, a“substituted phenyl” group must still comprise the phenyl moiety andcannot be modified by substitution, in this definition, to become, e.g.,a cyclohexyl group. In a broad aspect, the permissible substituentsinclude acyclic and cyclic, branched and unbranched, carbocyclic andheterocyclic, aromatic and nonaromatic substituents of organiccompounds. Illustrative substituents include, for example, thosedescribed herein. The permissible substituents can be one or more andthe same or different for appropriate organic compounds. For purposes ofthis invention, the heteroatoms such as nitrogen may have hydrogensubstituents and/or any permissible substituents of organic compoundsdescribed herein which satisfy the valencies of the heteroatoms. Thisinvention is not intended to be limited in any manner by the permissiblesubstituents of organic compounds.

Examples of substituents include, but are not limited to, lower alkyl,lower aryl, lower aralkyl, lower cyclic alkyl, lower heterocycloalkyl,hydroxy, lower alkoxy, lower aryloxy, perhaloalkoxy, aralkoxy, lowerheteroaryl, lower heteroaryloxy, lower heteroarylalkyl, lowerheteroaralkoxy, azido, amino, halogen, lower alkylthio, oxo, loweracylalkyl, lower carboxy esters, carboxyl, -carboxamido, nitro, loweracyloxy, lower aminoalkyl, lower alkylaminoaryl, lower alkylaryl, loweralkylaminoalkyl, lower alkoxyaryl, lower arylamino, lower aralkylamino,lower alkylsulfonyl, lower-carboxamidoalkylaryl, lower -carboxamidoaryl,lower hydroxyalkyl, lower haloalkyl, lower alkylaminoalkylcarboxy-,lower aminocarboxamidoalkyl-, cyano, lower alkoxyalkyl, lowerperhaloalkyl, lower arylalkyloxyalkyl, and the like.

EXAMPLES Example 1

All complexes were handled using standard Schlenk techniques or in aVacuum Atmospheres glove box under an argon or dinitrogen atmosphere.All solvents were dried, degassed, and stored over activated molecularsieves in a dinitrogen-filled glovebox. Pyrrole was distilled from CaH₂in an inert atmosphere and lithium pyrrolide was prepared usingpublished procedures. Mo(N-2,6-i-Pr₂C₆H₃)(CHCMe₂Ph)(OTf)₂DME,Mo(NAd)(CHR)(OTf)₂(DME), and Mo(N-2,6-Br₂-4-MeC₆H₂)(CHCMe₃)(OTf)₂(DME)were synthesized by published procedures. Elemental analyses wereperformed by Desert Analytics, Tucson, Ariz. Little or no competitivedeprotonation of the alkylidene to give an alkylidyne complex wasobserved. The compounds were sensitive to air and moisture and could berecrystallized readily from toluene or mixtures of pentane and ether.

Example 2 Synthesis of Mo(N-2,6-i-Pr₂C₆H₃)(CHCMe₃)(NC₄H₄)₂

The following procedure was used to prepare the title compound. To a−35° C. solution of 0.193 g (0.27 mmol) Mo(NAr)(CHCMe₃)(OTf)₂(DME) in 4mL diethyl ether was added 38.6 mg (0.53 mmol) of LiNC₄H₄ as a solid inone portion. The mixture was stirred at room temperature for 1 hour,then all volatiles were removed in vacuo. The resulting brown powder wasextracted with 5 mL of toluene and the solution was filtered throughcelite. The celite was washed with toluene (1 mL) and the resultingsolution was taken to dryness in vacuo. The product was recrystallizedfrom mixtures of pentane/toluene or pure toluene at −35° C. as a toluenesolvate. ¹H NMR (300 MHz, toluene-d₈) δ 13.5 (br s, 1H, MoCHR), 7-6.2 (vbr s, overlapping, 11H, Ar—H and NC₄H₄), 3.8-2.9 (br s, 2H, i-Pr), 1.3(br s, 6H, CMe₃), 1.1 (br s, 12H, i-Pr).

Example 3 Synthesis of Mo(N-2,6-i-Pr₂C₆H₃)(CHCMe₂Ph)(NC₄H₄)₂

The following procedure was used to prepare the title compound. LiNC₄H₄(410 mg, 5.62 mmol) was added as a solid in several small portions a−40° C. solution of 2.223 g (2.81 mmol) Mo(NAr)(CHCMe₂Ph)(OTf)₂(DME) in60 mL of diethyl ether. The mixture was stirred at room temperature for1 hour. All volatiles were removed in vacuo and the resulting powder wasextracted with 65 mL of a 1:1 mixture of toluene and pentane and thesolution was filtered through celite. The celite was washed with toluene(3×15 mL) and the resulting solution was reduced to dryness in vacuo.The solid was recrystallized from pentane −35° C.; yield 1.2 g (80%): ¹HNMR (toluene-d₈, 500 MHz) (223 K) δ 13.55 (s, 1H, MoCHR), 13.16 (s, 1H,MoCHR), 7.4-6.7 (m, Ar—H, NC₄H₄), 5.85 (s, 1H, NC₄H₄), 5.10 (s, 1H,NC₄H₄), 4.91 (s, 1H, NC₄H₄), 4.83 (s, 1H, NC₄H₄), 3.85 (sept, 2H, i-Prmethine), 2.85 (sept, 2H, i-Pr methine), 1.75 (s, 6H, MoCHCMe₂Ph), 1.71(s, 3H, MoCHCMe₂Ph), 1.68 (s, 3H, MoCHCMe₂Ph), 1.19 (br d, 12H,Ar-i-Pr), 1.12 (d, 3H, Ar-i-Pr), 1.03 (overlapping d, 6H, Ar-i-Pr), 0.55(d, 3H, Ar-i-Pr); (323 K): δ 13.18 (s, 1H, MoCHR), 7.33 (d, 2H,MoCHCMe₂Ar), 7.18 (t, 2H, MoCHCMe₂Ar), 7.05 (t, 1H, MoCHCMe₂Ar), 6.86(m, 3H, MoNAr), 6.44 (s, 4H, NC₄H₄), 6.14, (s, 4H, NC₄H₄), 3.22 (sept,2H, i-Pr methine), 1.56 (s, 6H, MoCHCMe₂Ar), 0.96 (d, 12H, i-Pr methyl).¹³C NMR (CD₂Cl₂, 126 MHz, 223 K): 313.9 (J_(CH) 122.8 Hz), 293.9 (J_(CH)121.3 Hz). Analysis calcd. For C₃₀H₃₇MoN₃ (found): C, 67.28 (67.38), H,6.96 (7.20), Mo, 17.91, N, 7.85 (7.70).

Example 3 Synthesis of Mo(NAd)(CHCMe₂Ph)(NC₄H₄)₂

The following procedure was used to prepare the title compound. LiNC₄H₄(169 mg, 2.32 mmol) was added as a solid in small portions to a −35° C.solution of 0.890 g (1.16 mmol) Mo(NAd)(CHCMe₂Ph)(OTf)₂(DME) in 50 mL ofdiethyl ether. The mixture was stirred at room temperature for 1.5 h,then all volatiles were removed in vacuo. The resulting brown powder wasextracted with toluene and the solution was filtered through celite. Thecelite was washed with toluene and the combined filtrates were taken todryness in vacuo. The off-white solid may be recrystallized from tolueneat −35° C.; yield 420 mg (2 crops, 71%): ¹H NMR (C₆D₆, 500 MHz, 293 K) δ13.6 (br s, 1H, MoCHR), 12.8 (br s, 1H, MoCHR), 7.5, (br s, 4H,MoCHCMe₂Ph), 7.0-4.7 (2 overlapping br s, MoCHCMe₂Ph and NC₄H₄), 1.8-1.6(br multiplet, 15H, MoNAd), 1.3 (br s, 6H, MoCHCMe₂Ph). ¹³C (CD₂Cl₂ 126MHz, 223K): 316.1 (J_(CH) 118.2 Hz), 295.5 (J_(CH) 111.3 Hz). Analysiscalcd. For C₂₈H₃₅MoN₃ (found): C, 66.00 (65.10), H, 6.92 (6.60), Mo,18.83, N, 8.25 (7.04).

Example 4 Synthesis of Mo(N-2,6-Br₂-4-MeC₆H₂)(CHCMe₃)(NC₄H₄)₂

The following procedure was used to prepare the title compound. LiNC₄H₄(35.4 mg, 0.485 mmol) in diethyl ether (˜2 mL) was added to a −40° C.solution of 0.198 g (0.243 mmol) Mo(NAr)(CHCMe₃)(OTf)₂(DME) in 3 mL ofdichloromethane. The mixture was stirred at room temperature for 1 hourand all volatiles were removed in vacuo. The resulting red-brown powderwas extracted with benzene and the solution was filtered through celite.The celite was washed with benzene and the combined filtrates were takento dryness in vacuo. The product was recrystallized from pentanecontaining a few drops of benzene at −35° C.; yield 94 mg (62%): ¹H NMR(300 MHz, C₆D₆, 293 K) δ 13.4 (br s, 1H MoCHR), 6.8-6.4 (br overlappings, 10H, MoNAr and NC₄H₄), 3.1 (s, 3H, MoNAr methyl), 1.4 (br s, 9H,MoCHCMe₃). Analysis calcd. For C₂₀H₂₃MoBr₂N₃ (found): C, 42.81 (42.52),H, 4.13 (4.12), Mo, 17.10, Br, 28.48, N, 7.49 (6.83).

Example 5 Synthesis of Mo(NAd)(CHCMe₂Ph)(NC₄H₄)₂(PMe₃)

The following procedure was used to prepare the title compound. Excesstrimethylphosphine (50 μL) was added to 150 mg ofMo(NAd)(CHCMe₂Ph)(NC₄H₄)₂ in diethyl ether. The mixture was stirred atroom temperature for 30 minutes and the solvent was removed in vacuo.Mo(NAd)(CHCMe₂Ph)(NC₄H₄)₂(PMe₃) was crystallized from pentane as orangeblocks; yield 100 mg (58%): NMR (¹H, 300 MHz, C₆D₆) δ 12.49 (d, 1H,J_(H-P) 4.8 Hz, CHCMe₂Ph), 8.41 (m, 2H, Ar), 7.05 (m, 6H, Ar), 6.80 (s,4H, NC₄H₄), 6.40 (s, 4H, NC₄H₄), 2.43 (s, 6H), 1.82 (s, 6H), 1.73 (s,3H, Ad), 1.35 (s, 6H), 0.46 (d, 9H, J_(HP) 9.2 Hz, PMe₃); ¹³C NMR (C₆D₆)δ 301.73 (d, MoCHCMe₂Ph, ²J_(C-P) 19.5 Hz), 148, 132.19, 129.13, 126.37,125.96, 109.16, 108.62, 42.22, 36.21, 30.03, 16.50 (d, PMe₃, J_(C-P) 25Hz). Analysis calcd. For C₃₁H₄₄MoN₃P (found): C, 63.58 (63.37), H, 7.57(7.45), Mo, 16.38, N, 7.18 (6.04), P, 5.29.

Example 6

The reactivity of {Mo(NR)(CHCMe₂R′)(NC₄H₄)₂}₂ species towards a Lewisacid (e.g., B(C₆F₅)₃) and a Lewis base (e.g., PMe₃) was observed by NMR.

For example, Mo(N-2,6-i-Pr₂C₆H₃)(CHCMe₂Ph)(η¹-NC₄H₄)(η⁵-C₄H₄NB(C₆F₅)₃was synthesized according to the following procedure. To 23.0 mg (0.021mmol) of {Mo(N-2,6-i-Pr₂C₆H₃)(CHCMe₂Ph)(NC₄H₄)₂}₂ in ˜0.25 mL of C₆D₆was added B(C₆F₅)₃ (22 mg, 0.043 mmol) in ca. 0.25 mL C₆D₆. The solutionwas transferred to a Teflon-sealed NMR tube and the ¹H NMR spectrum wasrecorded. The Lewis acid B(C₆F₅)₃ was observed to react immediately with{Mo(NAr)(CHCMe₂Ph)(NC₄H₄)₂}₂ to yield a proposed mixture of syn and antialkylidenes of the adduct shown in FIG. 3. The four η⁵-pyrrolyl protonsin the major (syn) isomer were found at 7.7, 7.2, 5.7, and 5.4 ppm inbenzene-d₆. ¹H NMR (500 MHz, 293 K) δ 13.89 (s, 1H, MoCHR minor isomer),13.08 (s, 1H, MoCHR major isomer), 7.72 (br s, 1H, η⁵-C₄H₄NB(C₆F₅)₃),7.28 (br s, 1H, η⁵-C₄H₄NB(C₆F₅)₃), 7.08 (m, 4H, MoCHCMe₂Ph), 7.02 (d,J_(HH)7.6 Hz, 2H, η⁵-NC₄H₄), 6.87 (m, 1H, MoCHCMe₂Ph), 6.78 (d,J_(HH)7.6 Hz, 2H, η¹-NC₄H₄), 5.78 (br s, 1H, η⁵-C₄H₄NB(C₆F₅)₃), 5.41,(br s, 1H, η⁵-C₄H₄NB(C₆F₅)₃), 2.82 (br s, 2H, i-Pr methine), 1.51 (s,3H, MoCHCMe₂Ph), 1.25 (s, 3H, MoCHCMe₂Ph), 0.92 (br mult, 12H, i-Prmethyls).

Addition of one equivalent of PMe₃ to Mo(NAd)(CHCMe₂Ph)(NC₄H₄)₂ using asimilar procedure resulted in immediate formation ofsyn-Mo(NAd)(CHCMe₂Ph)(η¹-NC₄H₄)₂(PMe₃), wherein the alkylidene protonresonance was observed at 12.49 ppm with J_(HP)=5 Hz. An X-raystructural study showed that trimethylphosphine was bound to one of theCN_(imido)N_(pyrrolyl) faces of the pseudotetrahedral species, which isthe face analogous to the CNO face where trimethylphosphine is observedto bind in bisalkoxide species.

Example 7

The NMR spectra of the catalyst precursor complexes were then studied.The dipyrrolyl complexes were observed to be fluxional on the proton NMRtime scale. At 22° C., the spectra contained broad resonances, forexample, for Mo(NAr)(CHCMe₂Ph)(NC₄H₄)₂ in toluene-d₈ (at 500 MHz), asshown in FIG. 5. At high temperature, one alkylidene resonance at 13.3ppm and two pyrrolyl resonances at ˜6.1 and ˜6.3 ppm were observed. Atlow temperatures two alkylidene resonances at ˜13.2 and ˜13.6 ppm wereobserved in a 1:1 ratio and the pyrrolyl proton resonances were resolvedinto an obscured set of resonances downfield of 6.3 ppm, along with apattern of four sharp resonances near 5 ppm. No fluoride resonance wereobserved in the ¹⁹F NMR spectrum, and no solvent resonances wereobserved in the ¹H NMR spectrum upon addition of trimethylphosphine,which yielded a base adduct. A ¹³C NMR spectrum ofMo(NAr)(CHCMe₂Ph)(NC₄H₄)₂ at −50° C. in methylene chloride-d₂ revealedresonances at 313.9 ppm (J_(CH)=122.8 Hz) and 293.9 ppm (J_(CH)=121.3Hz), characteristic of syn alkylidene species.

The NMR spectra at high-temperatures were consistent with a CS symmetricMo(NR)(CHCMe₂R′)(η¹-NC₄H₄)₂ species on the NMR time scale in which thepyrrolyl ligands were η¹ on average and rotated rapidly about the Mo—Nbonds. Variable temperature spectra were identical at differentconcentrations, indicating that a small fraction of the dimer haddissociated into monomers in which interconversion of η¹-NC₄H₄ andη⁵-NC₄H₄ ligands was facile.

Example 8

The reactivity of {Mo(NR)(CHCMe₂R′)(NC₄H₄)₂}₂ species towards alcoholswas observed. The molybdenum catalyst precursor (ca. 0.02 mmol) wasdissolved in 0.2 mL of C₆D₆, and an equimolar amount of diol or,alternatively, two equivalents of alcohol in 0.3 mL of C₆D₆, werecombined in a Teflon-sealed NMR tube. The ¹H NMR spectrum was recordedwithin 15 minutes. All diols and alcohols examined proceeded tocompletion by the time the ¹H NMR spectrum was recorded.

Addition of two equivalents of monoalcohols (e.g., Me₃COH or(CF₃)₂MeCOH) or one equivalent of a biphenol or binaphthol to ˜10 mMsolutions of the Mo(NR)(CHCMe₂R′)(NC₄H₄)₂ (NR=NAd or NAr) speciesresulted in rapid formation of two equivalents of pyrrole and thecorresponding bisalkoxide or diolate complexes. The reaction was rapidand proceeded in ˜100% yield in all combinations screened, including thesterically-challenging combination of 2,6-diisopropylphenylimidoprecursor reacting with H₂[Biphen](H₂[Biphen]=3,3′-Di-t-butyl-5,5′,6,6′-tetramethyl-1,1′-Biphenyl-2,2′-diol).In the case of 3,3′-bis(2,4,6-triisopropylphenyl)-2,2′-binaphthol, theresulting binaphtholate appeared to bind one equivalent of pyrroleweakly, but the corresponding THF adduct was generated immediately uponaddition of one or more equivalents of THF. In some cases, catalyststhat have been isolated only as THF adducts, or that have proven to betoo unstable to isolate, may be prepared from dipyrrolyl complexes.

Example 9 Synthesis and Catalytic Activity ofMo(N-2,6-Br₂-4-MeC₆H₂)(CHCMe₃)[rac-Biphen]

Mo(N-2,6-Br₂-4-MeC₆H₂)(CHCMe₃)[Biphen] was prepared according to methodsas described herein and was subsequently evaluated for its catalyticactivity. Previous attempts to prepare this species through addition ofK₂[Biphen] to Mo(N-2,6-Br₂-4-MeC₆H₂)(CHCMe₃)(OTf)₂(DME) did not producethe desired species in pure form and/or in a practical yield. However,using the methods described herein,Mo(N-2,6-Br₂-4-MeC₆H₂)(CHCMe₃)(NC₄H₄)₂ reacted with rac-H₂[Biphen] inbenzene rapidly to yield the Mo(N-2,6-Br₂-4-MeC₆H₂)(CHCMe₃)[rac-Biphen]species in high yield. The alkylidene proton inMo(N-2,6-Br₂-4-MeC₆H₂)(CHCMe₃)[rac-Biphen] was found at 11.3 ppm with aJ_(CH) coupling constant of 132.6 Hz, consistent with a syn alkylideneisomer. The catalytic activity of in situ preparedMo(N-2,6-Br₂-4-MeC₆H₂)(CHCMe₃)[rac-Biphen] was confirmed through thering-closing metathesis of ˜80 equivalents of diallyl ether todihydrofuran in 15 minutes at room temperature in C₆D₆.

The high reactivity of the {Mo(NR)(CHCMe₂R′)(NC₄H₄)₂}₂ species towardsalcohols and/or a Lewis acid or base (Example 6) further supported theconcept that a small fraction of the dimer had dissociated into monomersin which interconversion of η¹-NC₄H, and η⁵-NC₄H₄ ligands was facile.

Example 10

Crystals of the complexes were obtained and studied by X-raydiffraction. Low temperature diffraction data were collected on aSiemens Platform three-circle diffractometer coupled to a Bruker-AXSSMART Apex CCD detector with graphite-monochromated MoKα radiation(λ=0.71073 Å), performing φ and ω-scans. The structures were solved bydirect methods using SHELXS and refined against F² on all data byfull-matrix least squares with SHELXL-97. All non-hydrogen atoms wererefined anisotropically. All hydrogen atoms were included into the modelat geometrically calculated positions and refined using a riding model.The isotropic displacement parameters of all hydrogen atoms were fixedto 1.2 times the U value of the atoms they are linked to (1.5 times formethyl groups). Crystal and structural refinement data for the structureis listed below.

Crystals of{Mo(NAr)(syn-CHCMe₂Ph)(η⁵-NC₄H₄)(η¹-NC₄H₄)}{Mo(NAr)(syn-CHCMe₂Ph)(η¹-NC₄H₄)₂}(Identification Code: 06172) grown at −40° C. from a mixture of pentaneand toluene were coated with Paratone-N oil (an Exxon-Mobile™ product)in a dinitrogen-filled glovebox and examined under a microscope. Asuitable crystal measuring 0.10×0.08×0.03 mm³ was selected and mountedin a nylon loop. Initial examination of the data indicated that thespace group was P2₁/c. However, no reasonable solution could be obtainedvia direct methods or from the Patterson map. The program CELL_NOW wasused to re-determine the unit cell from 999 reflections sampled fromseveral regions in the hemisphere of data. The resulting, slightlydifferent, unit cell was used to integrate the data in the SAINTsoftware package in the triclinic setting. A solution in the space groupP1 (#1) was refined isotropically and the routines ADDSYM and NEWSYM inPlaton were used to confirm that the correct space group was indeedP2₁/c. Re-integration in the primitive, monoclinic setting followed byabsorption correction with the SADABS package yielded the data set fromwhich the correct initial solution was obtained. Confirmation of thespace group/setting was substantiated by the successful refinement ofthe structure and use of the ADDSYM and NEWSYM functions in the Platonsoftware package. FIG. 4 shows the thermal ellipsoid plot (50%probability level) of the structure of the dimer,{Mo(NAr)(syn-CHCMe₂Ph)(η¹-NC₄H₄)(η¹-NC₄H₄)}{Mo(NAr)(syn-CHCMe₂Ph)(η¹-NC₄H₄)₂}.

The X-ray structural studies of Mo(N-2,6-i-Pr₂C₆H₃)(CHCMe₂Ph)(NC₄H₄)₂showed that the compound existed as an unsymmetric dimer,{Mo(NAr)(syn-CHCMe₂Ph)(η⁵-NC₄H₄)(η¹-NC₄H₄)}{Mo(NAr)(syn-CHCMe₂Ph)(η¹-NC₄H₄)₂}, in which the nitrogen in theη⁵-pyrrolyl behaves as a donor to the other Mo (FIG. 4). The electroncount in the Mo(NAr)(syn-CHCMe₂Ph)(η⁵-NC₄H₄)(η¹-NC₄H₄) half was 18, andin the Mo(NAr)(syn-CHCMe₂Ph)(η¹-NC₄H₄)₂(donor) half was 16. TheMo(NAr)(syn-CHCMe₂Ph)(η¹-NC₄H₄)₂(donor) fragment was approximately asquare pyramid with the alkylidene in the apical position. Bonddistances and angles were listed in Table 1 and Table 2, respectively.The dimeric structure was consistent with the NMR spectra at lowtemperature, i.e., one half (containing Mo(2)) has no symmetry, whilethe second (containing Mo(1)) effectively has C_(s) symmetric. (FIG. 5)The four sharp resonances near 5 ppm were assigned to the four protonsin the η⁵-NC₄H₄ that is bound to a chiral metal center.

Table 3 shows the X-ray crystal data and structure refinement for{Mo(NAr)(CHR)(NC₄H₄)₂}₂. Table 4 shows the atomic coordinates (×10⁴) andequivalent isotropic displacement parameters (Å²×10³) for{Mo(NAr)(CHR)(NC₄H₄)₂}₂, where U(eq) is defined as one third of thetrace of the orthogonalized U^(ij) tensor. Table 5 shows the bondlengths [Å] and angles [°] for {Mo(NAr)(CHR)(NC₄H₄)₂}₂. Table 6 showsthe anisotropic displacement parameters (Å²×10³) for{Mo(NAr)(CHR)(NC₄H₄)₂}₂. The anisotropic displacement factor exponenttakes the form:

−2π²[h²a*²U¹¹+ . . . +2hka*b*U¹²].

Table 7 shows the hydrogen coordinates (×10⁴) and isotropic displacementparameters (Å²×10³) for {Mo(NAr)(CHR)(NC₄H₄)₂}2.

TABLE 1 Selected bond distances for {Mo(NAr)(CHR)(NC₄H₄)₂}₂. Bond Bonddistance (Å) Mo(1)—C(1A) 1.859(5) Mo(2)—C(1B) 1.912(5) Mo(1)—N(2A)2.082(4) Mo—N(3A) 2.097(4) Mo(2)—N(2B) 2.060(4) Mo(2)—N(3B) 2.479(4)Mo(1)—N(3B) 2.395(4) Mo(2)-pyrrolyl centroid 2.48 Mo(2)—N(2B) 2.060(4)Mo(1)—Mo(2) 4.53

TABLE 2 Selected bond angles for {Mo(NAr)(CHR)(NC₄H₄)₂}₂. Bond Bondsangles (°) N(1A)—Mo(1)—C(1A)  99.5(2) N(1A)—Mo(1)—N(3B) 155.16(16)N(2A)—Mo(1)—N(3A) 150.98(16) pyrrolyl centroid-Mo(2)—N(1B) 157.3N(1B)—Mo(2)—C(1B)  100.5(2) N(1B)—Mo(2)—N(2B) 101.80(17)

TABLE 3 Crystal data and structure refinement for{Mo(NAr)(CHR)(NC₄H₄)₂}₂. Identification code 06172 Empirical formulaC₆₇H₈₂Mo₂N₆ Formula weight 1163.27 Temperature 100(2) K Wavelength0.71073 Å Crystal system Monoclinic Space group P2₁/c Unit celldimensions a = 24.903(12) Å α = 90° b = 12.723(5) Å β = 106.001(12)° c =19.434(9) Å γ = 90° Volume 5919(4) Å³ Z 4 Density (calculated) 1.305Mg/m³ Absorption coefficient 0.469 mm⁻¹ F(000) 2440 Crystal size 0.10 ×0.08 × 0.03 mm³ Theta range for data collection 1.70 to 21.97°. Indexranges −26 <= h <= 25, 0 <= k <= 13, 0 <= l <= 20 Reflections collected7216 Independent reflections 7216 [R(int) = 0.1879] Completeness totheta = 21.97° 99.6% Absorption correction Empirical Max. and min.transmission 0.9861 and 0.9546 Refinement method Full-matrixleast-squares on F² Data/restraints/parameters 7216/0/670Goodness-of-fit on F² 1.013 Final R indices [I > 2sigma(I)] R1 = 0.0412,wR2 = 0.0775 R indices (all data) R1 = 0.0753, wR2 = 0.0901 Largestdiff. peak and hole 0.590 and −0.534 e · Å⁻³

TABLE 4 Atomic coordinates (× 10⁴) and equivalent isotropic displacementparameters (Å² × 10³) for {Mo(NAr)(CHR)(NC₄H₄)₂}₂. U(eq) is defined asone third of the trace of the orthogonalized U^(ij) tensor. x y z U(eq)Mo(1) 3042(1) 8833(1) 4794(1) 15(1) Mo(2) 1260(1) 9284(1) 3435(1) 16(1)N(1A) 3711(2) 8566(3) 5307(2) 15(1) N(2A) 2949(2) 7481(3) 4169(2) 18(1)N(3A) 2778(2) 9826(3) 5499(2) 16(1) N(1B)  573(2) 9542(3) 2975(2) 16(1)N(2B) 1584(2) 8780(3) 2624(2) 18(1) N(3B) 2048(2) 8621(3) 4418(2) 17(1)C(1A) 3201(2) 9782(4) 4150(3) 17(1) C(2A) 3661(2) 10288(4)  3889(3)21(1) C(3A) 3722(2) 9622(4) 3256(3) 29(2) C(4A) 4217(2) 10277(4) 4472(3) 26(1) C(5A) 3493(2) 11426(4)  3668(3) 17(1) C(6A) 3495(2)12174(4)  4195(3) 23(1) C(7A) 3377(2) 13223(4)  4019(3) 26(1) C(8A)3246(2) 13539(4)  3313(3) 28(2) C(9A) 3221(2) 12800(4)  2784(3) 26(1)C(10A) 3351(2) 11751(4)  2960(3) 24(1) C(11A) 2805(2) 7348(4) 3437(3)21(1) C(12A) 2658(2) 6321(4) 3270(3) 25(1) C(13A) 2708(2) 5785(4)3908(3) 25(1) C(14A) 2886(2) 6507(4) 4449(3) 22(1) C(15A) 2631(2)10869(4)  5439(3) 17(1) C(16A) 2388(2) 11154(4)  5966(3) 21(1) C(17A)2380(2) 10237(4)  6378(3) 23(1) C(18A) 2621(2) 9459(4) 6080(3) 21(1)C(19A) 4235(2) 8243(4) 5738(3) 16(1) C(20A) 4556(2) 7535(4) 5453(3)22(1) C(21A) 5056(2) 7183(4) 5908(3) 25(1) C(22A) 5231(2) 7515(4)6605(3) 29(2) C(23A) 4922(2) 8235(4) 6870(3) 29(1) C(24A) 4421(2)8623(4) 6443(3) 23(1) C(25A) 4377(2) 7171(4) 4677(3) 24(1) C(26A)4814(2) 7493(4) 4293(3) 31(2) C(27A) 4279(2) 5983(4) 4617(3) 34(2)C(28A) 4093(2) 9443(5) 6726(3) 33(2) C(29A) 4306(3) 10534(5)  6630(3)58(2) C(30A) 4091(3) 9295(5) 7494(3) 58(2) C(1B) 1561(2) 10676(4) 3538(3) 20(1) C(2B) 1398(2) 11805(4)  3341(3) 21(1) C(3B) 1753(2)12191(4)  2857(3) 30(2) C(4B)  779(2) 11925(4)  2919(3) 25(1) C(5B)1506(2) 12448(4)  4032(3) 18(1) C(6B) 1904(2) 13232(4)  4213(3) 24(1)C(7B) 1966(2) 13822(4)  4826(3) 29(1) C(8B) 1646(2) 13645(4)  5281(3)26(1) C(9B) 1259(2) 12844(4)  5127(3) 26(1) C(10B) 1194(2) 12252(4) 4514(3) 22(1) C(11B) 1845(2) 9337(4) 2197(3) 24(1) C(12B) 1867(2)8742(4) 1624(3) 28(1) C(13B) 1622(2) 7766(4) 1694(3) 26(1) C(14B)1454(2) 7811(4) 2298(3) 20(1) C(15B) 1666(2) 9114(4) 4704(3) 20(1)C(16B) 1160(2) 8570(4) 4521(3) 18(1) C(17B) 1234(2) 7679(4) 4127(3)18(1) C(18B) 1773(2) 7743(4) 4063(3) 18(1) C(19B)  16(2) 9695(4) 2584(3)17(1) C(20B) −395(2) 9841(4) 2951(3) 18(1) C(21B) −932(2) 10069(4) 2548(3) 22(1) C(22B) −1069(2)   10113(4)  1815(3) 22(1) C(23B) −669(2)9943(4) 1458(3) 26(1) C(24B) −115(2) 9740(4) 1835(3) 18(1) C(25B)−252(2) 9681(4) 3752(3) 22(1) C(26B) −623(2) 10295(5)  4123(3) 38(2)C(27B) −281(2) 8497(4) 3899(3) 29(2) C(28B)  320(2) 9543(4) 1433(3)22(1) C(29B)  362(2) 10463(4)   951(3) 31(2) C(30B)  190(2) 8524(4) 995(3) 26(1) C(1T) 6467(2) 4402(4) 3582(3) 26(1) C(2T) 5918(2) 4583(5)3559(3) 31(2) C(3T) 5741(2) 5558(5) 3710(3) 36(2) C(4T) 6107(3) 6385(5)3884(3) 33(2) C(5T) 6661(2) 6216(5) 3907(3) 30(1) C(6T) 6837(2) 5230(4)3765(3) 25(1) C(7T) 6658(3) 3336(4) 3424(3) 37(2)

TABLE 5 Bond lengths [Å] and angles [°] for {Mo(NAr)(CHR)(NC₄H₄)₂}₂.Mo(1)—N(1A) 1.725(4) C(12A)—C(13A) 1.391(7) Mo(1)—C(1A) 1.859(5)C(13A)—C(14A) 1.374(7) Mo(1)—N(2A) 2.082(4) C(15A)—C(16A) 1.374(7)Mo(1)—N(3A) 2.097(4) C(16A)—C(17A) 1.419(7) Mo(1)—N(3B) 2.395(4)C(17A)—C(18A) 1.366(7) Mo(2)—N(1B) 1.730(4) C(19A)—C(24A) 1.407(7)Mo(2)—C(1B) 1.912(5) C(19A)—C(20A) 1.414(7) Mo(2)—N(2B) 2.060(4)C(20A)—C(21A) 1.387(7) Mo(2)—C(16B) 2.373(5) C(20A)—C(25A) 1.523(7)Mo(2)—C(15B) 2.403(5) C(21A)—C(22A) 1.369(7) Mo(2)—C(17B) 2.456(5)C(22A)—C(23A) 1.384(7) Mo(2)—C(18B) 2.471(5) C(23A)—C(24A) 1.383(7)Mo(2)—N(3B) 2.479(4) C(24A)—C(28A) 1.518(7) N(1A)—C(19A) 1.404(6)C(25A)—C(27A) 1.531(7) N(2A)—C(11A) 1.379(6) C(25A)—C(26A) 1.535(7)N(2A)—C(14A) 1.379(6) C(28A)—C(30A) 1.507(8) N(3A)—C(15A) 1.373(6)C(28A)—C(29A) 1.516(8) N(3A)—C(18A) 1.375(6) C(1B)—C(2B) 1.513(7)N(1B)—C(19B) 1.400(6) C(2B)—C(5B) 1.532(7) N(2B)—C(14B) 1.383(6)C(2B)—C(3B) 1.537(7) N(2B)—C(11B) 1.383(6) C(2B)—C(4B) 1.542(7)N(3B)—C(15B) 1.376(6) C(5B)—C(6B) 1.382(7) N(3B)—C(18B) 1.390(6)C(5B)—C(10B) 1.394(7) C(1A)—C(2A) 1.519(7) C(6B)—C(7B) 1.380(7)C(2A)—C(4A) 1.530(7) C(7B)—C(8B) 1.362(7) C(2A)—C(3A) 1.534(7)C(8B)—C(9B) 1.378(7) C(2A)—C(5A) 1.536(7) C(9B)—C(10B) 1.381(7)C(5A)—C(10A) 1.386(7) C(11B)—C(12B) 1.359(7) C(5A)—C(6A) 1.396(7)C(12B)—C(13B) 1.407(7) C(6A)—C(7A) 1.389(7) C(13B)—C(14B) 1.352(7)C(7A)—C(8A) 1.379(7) C(15B)—C(16B) 1.395(7) C(8A)—C(9A) 1.382(7)C(16B)—C(17B) 1.409(7) C(9A)—C(10A) 1.394(7) C(17B)—C(18B) 1.383(7)C(11A)—C(12A) 1.371(7) C(19B)—C(24B) 1.403(7) C(19B)—C(20B) 1.411(7)N(2B)—Mo(2)—C(15B) 127.86(16) C(20B)—C(21B) 1.381(7) C(16B)—Mo(2)—C(15B)33.95(16) C(20B)—C(25B) 1.513(7) N(1B)—Mo(2)—C(17B) 105.61(17)C(21B)—C(22B) 1.373(7) C(1B)—Mo(2)—C(17B) 141.38(19) C(22B)—C(23B)1.378(7) N(2B)—Mo(2)—C(17B) 103.58(16) C(23B)—C(24B) 1.395(7)C(16B)—Mo(2)—C(17B) 33.87(16) C(24B)—C(28B) 1.519(7) C(15B)—Mo(2)—C(17B)55.28(17) C(25B)—C(26B) 1.532(7) N(1B)—Mo(2)—C(18B) 135.13(17)C(25B)—C(27B) 1.539(7) C(1B)—Mo(2)—C(18B) 123.28(19) C(28B)—C(29B)1.522(7) N(2B)—Mo(2)—C(18B) 82.71(16) C(28B)—C(30B) 1.536(7)C(16B)—Mo(2)—C(18B) 54.77(17) C(1T)—C(2T) 1.376(7) C(15B)—Mo(2)—C(18B)53.65(17) C(1T)—C(6T) 1.381(7) C(17B)—Mo(2)—C(18B) 32.59(15) C(1T)—C(7T)1.496(7) N(1B)—Mo(2)—N(3B) 157.32(16) C(2T)—C(3T) 1.374(8)C(1B)—Mo(2)—N(3B) 91.72(18) C(3T)—C(4T) 1.372(8) N(2B)—Mo(2)—N(3B)95.18(15) C(4T)—C(5T) 1.385(8) C(16B)—Mo(2)—N(3B) 55.84(16) C(5T)—C(6T)1.381(7) C(15B)—Mo(2)—N(3B) 32.69(14) N(1A)—Mo(1)—C(1A) 99.5(2)C(17B)—Mo(2)—N(3B) 55.21(15) N(1A)—Mo(1)—N(2A) 96.24(16)C(18B)—Mo(2)—N(3B) 32.62(14) C(1A)—Mo(1)—N(2A) 98.82(19)C(19A)—N(1A)—Mo(1) 173.9(3) N(1A)—Mo(1)—N(3A) 99.65(17)C(11A)—N(2A)—C(14A) 105.8(4) C(1A)—Mo(1)—N(3A) 102.26(18)C(11A)—N(2A)—Mo(1) 131.2(3) N(2A)—Mo(1)—N(3A) 150.98(16)C(14A)—N(2A)—Mo(1) 121.2(3) N(1A)—Mo(1)—N(3B) 155.16(16)C(15A)—N(3A)—C(18A) 105.5(4) C(1A)—Mo(1)—N(3B) 105.19(18)C(15A)—N(3A)—Mo(1) 130.6(3) N(2A)—Mo(1)—N(3B) 77.85(14)C(18A)—N(3A)—Mo(1) 122.9(3) N(3A)—Mo(1)—N(3B) 77.54(14)C(19B)—N(1B)—Mo(2) 176.7(4) N(1B)—Mo(2)—C(1B) 100.5(2)C(14B)—N(2B)—C(11B) 105.7(4) N(1B)—Mo(2)—N(2B) 101.80(17)C(14B)—N(2B)—Mo(2) 122.4(3) C(1B)—Mo(2)—N(2B) 98.28(19)C(11B)—N(2B)—Mo(2) 130.4(4) N(1B)—Mo(2)—C(16B) 101.58(18)C(15B)—N(3B)—C(18B) 105.4(4) C(1B)—Mo(2)—C(16B) 113.26(19)C(15B)—N(3B)—Mo(1) 126.6(3) N(2B)—Mo(2)—C(16B) 136.06(17)C(18B)—N(3B)—Mo(1) 124.6(3) N(1B)—Mo(2)—C(15B) 128.59(18)C(15B)—N(3B)—Mo(2) 70.6(3) C(1B)—Mo(2)—C(15B) 86.18(19)C(18B)—N(3B)—Mo(2) 73.4(3) Mo(1)—N(3B)—Mo(2) 136.74(17)C(20A)—C(25A)—C(27A) 111.9(4) C(2A)—C(1A)—Mo(1) 145.1(4)C(20A)—C(25A)—C(26A) 110.2(4) C(1A)—C(2A)—C(4A) 111.2(4)C(27A)—C(25A)—C(26A) 110.3(4) C(1A)—C(2A)—C(3A) 106.5(4)C(30A)—C(28A)—C(29A) 109.5(5) C(4A)—C(2A)—C(3A) 108.6(4)C(30A)—C(28A)—C(24A) 114.9(5) C(1A)—C(2A)—C(5A) 108.6(4)C(29A)—C(28A)—C(24A) 110.1(5) C(4A)—C(2A)—C(5A) 109.7(4)C(2B)—C(1B)—Mo(2) 141.5(4) C(3A)—C(2A)—C(5A) 112.1(4) C(1B)—C(2B)—C(5B)108.3(4) C(10A)—C(5A)—C(6A) 118.3(5) C(1B)—C(2B)—C(3B) 107.4(4)C(10A)—C(5A)—C(2A) 122.2(5) C(5B)—C(2B)—C(3B) 112.0(4) C(6A)—C(5A)—C(2A)119.5(5) C(1B)—C(2B)—C(4B) 112.8(4) C(7A)—C(6A)—C(5A) 121.1(5)C(5B)—C(2B)—C(4B) 108.7(4) C(8A)—C(7A)—C(6A) 120.0(5) C(3B)—C(2B)—C(4B)107.6(4) C(7A)—C(8A)—C(9A) 119.5(5) C(6B)—C(5B)—C(10B) 116.8(5)C(8A)—C(9A)—C(10A) 120.6(5) C(6B)—C(5B)—C(2B) 123.3(5)C(5A)—C(10A)—C(9A) 120.4(5) C(10B)—C(5B)—C(2B) 119.9(5)C(12A)—C(11A)—N(2A) 109.8(5) C(7B)—C(6B)—C(5B) 120.9(5)C(11A)—C(12A)—C(13A) 107.7(5) C(8B)—C(7B)—C(6B) 121.6(5)C(14A)—C(13A)—C(12A) 106.6(5) C(7B)—C(8B)—C(9B) 118.7(5)C(13A)—C(14A)—N(2A) 110.2(5) C(8B)—C(9B)—C(10B) 120.0(5)N(3A)—C(15A)—C(16A) 110.7(5) C(9B)—C(10B)—C(5B) 121.8(5)C(15A)—C(16A)—C(17A) 106.3(5) C(12B)—C(11B)—N(2B) 109.8(5)C(18A)—C(17A)—C(16A) 106.2(5) C(11B)—C(12B)—C(13B) 107.2(5)C(17A)—C(18A)—N(3A) 111.2(5) C(14B)—C(13B)—C(12B) 107.0(5)N(1A)—C(19A)—C(24A) 118.9(4) C(13B)—C(14B)—N(2B) 110.3(5)N(1A)—C(19A)—C(20A) 119.1(4) N(3B)—C(15B)—C(16B) 110.3(4)C(24A)—C(19A)—C(20A) 122.0(5) N(3B)—C(15B)—Mo(2) 76.7(3)C(21A)—C(20A)—C(19A) 117.5(5) C(16B)—C(15B)—Mo(2) 71.8(3)C(21A)—C(20A)—C(25A) 120.0(5) C(15B)—C(16B)—C(17B) 107.1(5)C(19A)—C(20A)—C(25A) 122.5(5) C(15B)—C(16B)—Mo(2) 74.2(3)C(22A)—C(21A)—C(20A) 121.0(5) C(17B)—C(16B)—Mo(2) 76.3(3)C(21A)—C(22A)—C(23A) 120.9(5) C(18B)—C(17B)—C(16B) 106.0(5)C(24A)—C(23A)—C(22A) 121.0(5) C(18B)—C(17B)—Mo(2) 74.3(3)C(23A)—C(24A)—C(19A) 117.5(5) C(16B)—C(17B)—Mo(2) 69.8(3)C(23A)—C(24A)—C(28A) 121.0(5) C(17B)—C(18B)—N(3B) 111.1(4)C(19A)—C(24A)—C(28A) 121.5(5) C(17B)—C(18B)—Mo(2) 73.1(3)N(3B)—C(18B)—Mo(2) 74.0(3) N(1B)—C(19B)—C(24B) 118.7(5)N(1B)—C(19B)—C(20B) 119.5(5) C(24B)—C(19B)—C(20B) 121.7(5)C(21B)—C(20B)—C(19B) 117.7(5) C(21B)—C(20B)—C(25B) 121.9(5)C(19B)—C(20B)—C(25B) 120.3(4) C(22B)—C(21B)—C(20B) 121.4(5)C(21B)—C(22B)—C(23B) 120.6(5) C(22B)—C(23B)—C(24B) 120.8(5)C(23B)—C(24B)—C(19B) 117.7(5) C(23B)—C(24B)—C(28B) 120.2(5)C(19B)—C(24B)—C(28B) 122.1(5) C(20B)—C(25B)—C(26B) 114.4(4)C(20B)—C(25B)—C(27B) 108.3(4) C(26B)—C(25B)—C(27B) 110.3(5)C(24B)—C(28B)—C(29B) 111.7(4) C(24B)—C(28B)—C(30B) 110.7(4)C(29B)—C(28B)—C(30B) 110.4(4) C(2T)—C(1T)—C(6T) 117.9(5)C(2T)—C(1T)—C(7T) 120.9(5) C(6T)—C(1T)—C(7T) 121.2(5) C(3T)—C(2T)—C(1T)121.3(6) C(4T)—C(3T)—C(2T) 120.9(6) C(3T)—C(4T)—C(5T) 118.5(6)C(6T)—C(5T)—C(4T) 120.3(5) C(1T)—C(6T)—C(5T) 121.2(5)

TABLE 6 Anisotropic displacement parameters (Å² × 10³) for{Mo(NAr)(CHR)(NC₄H₄)₂}₂. The anisotropic displacement factor exponenttakes the form: −2π²[h² a*²U¹¹ + . . . + 2 h k a* b* U¹²] U¹¹ U²² U³³U²³ U¹³ U¹² Mo(1) 15(1) 15(1) 15(1)    0(1)    1(1)    1(1) Mo(2) 14(1)15(1) 18(1)  −1(1)    2(1)    0(1) N(1A) 15(2) 14(3) 13(2)    2(2)   2(2)    0(2) N(2A) 13(2) 17(3) 18(3)    3(2)  −2(2)    2(2) N(3A)14(2) 12(3) 18(3)  −1(2)    0(2)    4(2) N(1B) 15(3) 20(3) 11(2)    5(2)   0(2)    0(2) N(2B) 18(2) 16(3) 19(3)  −3(2)    6(2)    0(2) N(3B)19(3) 12(3) 18(3)  −3(2)    1(2)  −1(2) C(1A) 17(3) 19(3) 13(3)    2(2)   1(2)    6(2) C(2A) 21(3) 20(3) 21(3)    5(3)    3(3)    1(3) C(3A)38(4) 25(3) 28(3)    5(3)   17(3)    1(3) C(4A) 21(3) 25(3) 32(4)   5(3)    6(3)  −1(3) C(5A)  9(3) 20(3) 24(3)  −3(3)    7(2)  −6(2)C(6A) 22(3) 26(4) 25(3)    2(3)   11(3)  −2(3) C(7A) 28(4) 23(4) 29(4) −6(3)    9(3)  −1(3) C(8A) 22(3) 17(3) 47(4)   11(3)   14(3)    3(3)C(9A) 22(3) 34(4) 21(3)   17(3)    5(3)    2(3) C(10A) 23(3) 31(4) 17(3)   9(3)    6(3)    2(3) C(11A) 15(3) 24(4) 24(4)    0(3)    4(3)  −2(3)C(12A) 25(3) 25(4) 24(4)  −9(3)    5(3)  −4(3) C(13A) 23(3) 14(3) 37(4) −4(3)    4(3)  −2(3) C(14A) 16(3) 27(4) 22(3)    7(3)    3(3)    8(3)C(15A) 14(3) 16(3) 18(3)  −2(2)  −1(2)  −1(2) C(16A) 24(3) 16(3) 19(3) −8(3)  −2(3)    5(3) C(17A) 20(3) 37(4) 15(3)  −5(3)    5(3)    3(3)C(18A) 21(3) 24(3) 19(3)    3(3)    5(3)    0(3) C(19A) 12(3) 18(3)17(3)    4(3)    1(3)  −1(2) C(20A) 18(3) 21(3) 30(4)    2(3)   11(3) −3(3) C(21A) 17(3) 25(3) 32(4)    6(3)    6(3)    4(3) C(22A) 12(3)34(4) 35(4)    9(3)  −1(3)  −2(3) C(23A) 20(3) 35(4) 25(3)    2(3) −3(3)  −3(3) C(24A) 16(3) 26(4) 26(4)    5(3)    5(3)  −4(3) C(25A)19(3) 25(3) 28(4)    0(3)    9(3)    5(3) C(26A) 27(3) 38(4) 29(4) −6(3)    9(3)    4(3) C(27A) 30(4) 30(4) 41(4)  −7(3)    8(3)    4(3)C(28A) 23(3) 43(4) 26(4)  −8(3)  −7(3)    5(3) C(29A) 99(4) 47(3) 44(3)   1(3)   44(3)   13(3) C(30A) 99(4) 47(3) 44(3)    1(3)   44(3)   13(3)C(1B) 17(3) 15(3) 26(3)  −2(3)    4(2)    0(2) C(2B) 16(3) 24(3) 23(3)   6(3)    7(3)    0(3) C(3B) 37(4) 21(3) 31(4)    2(3)   12(3)  −4(3)C(4B) 24(3) 24(3) 22(3)  −3(3)  −1(3)    1(3) C(5B) 13(3) 14(3) 24(3)   8(3)    1(3)    9(3) C(6B) 21(3) 25(3) 25(3)    1(3)    6(3)  −3(3)C(7B) 19(3) 23(3) 35(4)  −6(3)  −7(3)  −5(3) C(8B) 28(4) 26(4) 23(3) −2(3)    3(3)    2(3) C(9B) 22(3) 32(4) 20(3)  −1(3)    2(3)    3(3)C(10B) 14(3) 18(3) 33(4)    2(3)    4(3)  −6(2) C(11B) 22(3) 23(3) 31(4)   6(3)  13(3)  −2(3) C(12B) 27(3) 34(4) 28(4)    1(3)   17(3)  −4(3)C(13B) 28(3) 29(4) 18(3)  −6(3)    4(3)    2(3) C(14B) 18(3) 17(3) 23(3) −3(3)    2(3)  −1(2) C(15B) 22(3) 20(3) 17(3)    0(2)    4(3)    8(3)C(16B) 19(3) 23(3) 15(3)    0(2)    9(3)    0(3) C(17B) 13(3) 19(3)18(3)    2(3)  −1(2)    1(2) C(18B) 17(3) 17(3) 18(3)    0(2)    0(3)   4(2) C(19B) 21(3)  6(3) 21(3)  −1(2)    1(3)    2(2) C(20B) 18(3)10(3) 25(3)  −6(2)    3(3)    3(2) C(21B) 21(3) 22(3) 24(4)  −2(3)   8(3)  −3(3) C(22B) 15(3) 18(3) 30(4)  −2(3)    0(3)  −1(2) C(23B)31(4) 25(4) 17(3)    0(3)    0(3)  −6(3) C(24B) 18(3) 15(3) 20(3)   1(2)    2(3)  −4(2) C(25B) 12(3) 31(4) 19(3)  −8(3)    0(2)    5(3)C(26B) 35(4) 53(4) 25(4) −11(3)    6(3)    8(3) C(27B) 29(4) 36(4) 18(3)   7(3)    3(3)  −6(3) C(28B) 19(3) 27(3) 14(3)    1(3)  −3(2)  −7(3)C(29B) 43(4) 34(4) 19(3)    1(3)   12(3)  −4(3) C(30B) 23(3) 31(4) 23(3)   2(3)    2(3)    0(3) C(1T) 25(4) 28(4) 21(3)    6(3)    3(3)    0(3)C(2T) 26(4) 44(4) 20(3)    2(3)    4(3) −12(3) C(3T) 25(4) 52(5) 31(4)   3(3)    7(3)    8(4) C(4T) 42(4) 37(4) 23(4)    4(3)   11(3)   13(3)C(5T) 36(4) 30(4) 23(3)    5(3)    8(3)  −5(3) C(6T) 19(3) 30(4) 28(3)   4(3)    7(3)    3(3) C(7T) 47(4) 26(4) 38(4)    5(3)   12(3)  −5(3)

TABLE 7 Hydrogen coordinates (×10⁴) and isotropic displacementparameters (Å² × 10³) for {Mo(NAr)(CHR)(NC₄H₄)₂}₂. x y z U(eq) H(10B)2855 10063 3872 20 H(10C) 3369 9623 2878 43 H(10D) 3820 8899 3417 43H(10E) 4018 9918 3071 43 H(11C) 4184 10700 4880 39 H(11D) 4511 105734281 39 H(11E) 4314 9552 4629 39 H(57A) 3579 11962 4681 28 H(25A) 338613723 4385 32 H(44A) 3175 14258 3192 34 H(19A) 3113 13009 2296 31 H(39A)3344 11255 2592 28 H(58A) 2807 7886 3099 25 H(17A) 2543 6029 2802 30H(9A) 2634 5062 3960 30 H(50A) 2955 6357 4945 27 H(28A) 2690 11330 508320 H(15A) 2252 11831 6039 26 H(10L) 2236 10175 6781 28 H(11A) 2672 87576252 26 H(10F) 5280 6704 5734 30 H(10A) 5570 7248 6910 34 H(10K) 50558465 7352 34 H(27A) 4017 7529 4433 28 H(61A) 4871 8256 4333 47 H(61B)4683 7296 3787 47 H(61C) 5167 7134 4515 47 H(10H) 3997 5788 4860 50H(10I) 4629 5616 4841 50 H(10J) 4147 5784 4111 50 H(8A) 3697 9403 642640 H(20B) 4091 11058 6811 88 H(20C) 4264 10663 6120 88 H(20D) 4701 105886896 88 H(48A) 3868 9852 7630 88 H(48B) 4475 9327 7804 88 H(48C) 39288609 7549 88 H(46A) 1943 10649 3805 23 H(12A) 2150 12128 3113 44 H(12B)1664 12928 2729 44 H(12C) 1671 11763 2421 44 H(65A) 542 11688 3216 37H(65B) 702 11499 2482 37 H(65C) 699 12665 2790 37 H(22A) 2138 13367 391128 H(91A) 2239 14364 4934 35 H(52A) 1689 14067 5696 32 H(81A) 1038 126985443 31 H(86A) 929 11697 4417 27 H(24A) 1988 10030 2290 29 H(10G) 20208948 1248 34 H(80A) 1582 7186 1376 31 H(54A) 1273 7257 2474 24 H(11F)1755 9717 5047 24 H(55A) 839 8696 4726 22 H(11G) 970 7075 3981 21 H(11B)1952 7195 3831 22 H(45A) −1213 10197 2784 26 H(20A) −1442 10263 1550 27H(41A) −771 9965 950 31 H(26A) 143 9915 3963 26 H(90A) −598 11048 402857 H(90B) −496 10170 4640 57 H(90C) −1011 10062 3937 57 H(71A) −37 81153668 43 H(71B) −666 8251 3707 43 H(71C) −159 8371 4417 43 H(78A) 6909456 1795 26 H(83A) 452 11105 1239 47 H(83B) 5 10554 586 47 H(83C) 65710323 718 47 H(31A) 169 7937 1313 40 H(31B) 486 8388 764 40 H(31C) −1688597 629 40 H(2TA) 5656 4024 3438 37 H(3TA) 5359 5660 3693 43 H(4TA)5983 7059 3986 40 H(5TA) 6920 6779 4021 36 H(6TA) 7220 5121 3794 31H(7TA) 7060 3354 3471 55 H(7TB) 6456 3131 2935 55 H(7TC) 6582 2826 376455

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified unless clearly indicated to the contrary. Thus,as a non-limiting example, a reference to “A and/or B.” when used inconjunction with open-ended language such as “comprising” can refer, inone embodiment, to A without B (optionally including elements other thanB); in another embodiment, to B without A (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” and the like are to be understoodto be open-ended, i.e., to mean including but not limited to. Only thetransitional phrases “consisting of” and “consisting essentially of”shall be closed or semi-closed transitional phrases, respectively, asset forth in the United States Patent Office Manual of Patent ExaminingProcedures, Section 2111.03.

1. A composition of matter, comprising: a compound having the structure,

wherein M is Mo or W; R¹ is alkyl, heteroalkyl, aryl, or heteroaryl,optionally substituted; R² and R³ can be the same or different and arehydrogen, alkyl, heteroalkyl, aryl, or heteroaryl, optionallysubstituted; R⁴ and R⁵ can be the same or different and are heteroalkylor heteroaryl, optionally substituted, or R⁴ and R⁵ are joined togetherto form a bidentate ligand with respect to M, optionally substituted;and wherein R⁴ and R⁵ each comprise at least one nitrogen atom.
 2. Acomposition as in claim 1, wherein M is Mo.
 3. A composition as in claim1, wherein R⁴ and R⁵ each coordinate M via a nitrogen atom.
 4. Acomposition as in claim 1, wherein R⁴ and R⁵ can be the same ordifferent and are heteroaryl groups comprising at least one nitrogenring atom.
 5. A composition as in claim 1, wherein R⁴ and R⁵ can be thesame or different and are pyrrolyl, pyrazolyl, pyridinyl, pyrazinyl,pyrimidinyl, imidazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl,thiazolyl, isothiazolyl, indolyl, indazolyl, carbazolyl, or substitutedderivatives thereof, or R⁴ and R⁵ are joined together to form abiphenolate or binaphtholate group.
 6. A composition as in claim 1,wherein R⁴ and R⁵ are pyrrolyl groups.
 7. A composition as in claim 1,wherein at least one of R⁴ and R⁵ is a chiral ligand, or R⁴ and R⁵ arejoined together to form a chiral ligand.
 8. A composition as in claim 1,wherein R¹ is substituted aryl.
 9. A composition as in claim 1, whereinR¹ is a monosubstituted aryl, 2,6-disubstituted aryl, or2,4,6-trisubstituted aryl.
 10. A composition as in claim 1, wherein,when R² is hydrogen, R³ is alkyl, heteroalkyl, aryl, or heteroaryl,optionally substituted, or, when R³ is hydrogen, R² is alkyl,heteroalkyl, aryl, or heteroaryl, optionally substituted.
 11. Acomposition as in claim 1, wherein M is Mo; R¹ is substituted aryl; R²is alkyl, optionally substituted; R³ is hydrogen; R⁴ and R⁵ areheteroaryl, optionally substituted, or R⁴ and R⁵ are joined together toform a bidentate ligand with respect to M, optionally substituted; andwherein R⁴ and R⁵ each comprise at least one nitrogen atom.
 12. Acomposition as in claim 1, wherein the compound has the structure,


13. A method for synthesizing a catalyst, comprising: providing acompound having the structure,

wherein M is Mo or W; R¹ is alkyl, heteroalkyl, aryl, or heteroaryl,optionally substituted; R² and R³ can be the same or different and arehydrogen, alkyl, heteroalkyl, aryl, or heteroaryl, optionallysubstituted; R⁴ and R⁵ can be the same or different and are heteroalkylor heteroaryl, optionally substituted, or R⁴ and R⁵ are joined togetherto form a bidentate ligand with respect to M, optionally substituted;and wherein R⁴ and R⁵ each comprise at least one nitrogen atom; andreacting the compound with an oxygen-containing ligand such that theoxygen-containing ligand replaces R⁴ and R⁵ to form a catalyst.
 14. Amethod as in claim 13, wherein the oxygen-containing ligand is aheteroaryl or heteroalkyl group comprising at least one oxygen ringatom.
 15. A method as in claim 13, wherein the oxygen-containing ligandis a bidentate ligand.
 16. A method as in claim 13, wherein theoxygen-containing ligand is a chiral ligand.
 17. A method as in claim13, wherein the oxygen-containing ligand is attached to a surface via acovalent or a non-covalent bond.
 18. A method as in claim 13, whereinthe reacting occurs at a temperature of less than 100° C.
 19. A methodas in claim 13, wherein the reacting occurs at a temperature of lessthan 80° C.
 20. A method as in claim 13, wherein the reacting occurs ata temperature of less than 60° C.
 21. A method as in claim 13, whereinthe reacting occurs at a temperature of less than 40° C.
 22. A method asin claim 13, wherein the reacting occurs at a temperature of less than25° C.
 23. A method as in claim 13, wherein the reacting occurs with ayield of at least 50%.
 24. A method as in claim 13, wherein the reactingoccurs with a yield of at least 60%.
 25. A method as in claim 13,wherein the reacting occurs with a yield of at least 70%.
 26. A methodas in claim 13, wherein the reacting occurs with a yield of at least80%.
 27. A method as in claim 13, wherein the reacting occurs with ayield of at least 90%.
 28. A method as in claim 13, wherein the reactingoccurs with a yield of at least 95%.
 29. A method as in claim 13,further comprising, catalyzing a reaction with the catalyst, wherein thecatalyst is present at a concentration of less than 100 mM.
 30. A methodas in claim 13, further comprising, catalyzing a reaction with thecatalyst, wherein the catalyst is present at a concentration of lessthan 50 mM.
 31. A method as in claim 13, further comprising, catalyzinga reaction with the catalyst, wherein the catalyst is present at aconcentration of less than 10 mM.
 32. A method as in claim 18, whereinthe reaction is a carbon-carbon bond forming reaction.
 33. A method asin claim 18, wherein the reaction is an olefin metathesis reaction. 34.A method as in claim 20, wherein the olefin metathesis reaction is aring-closing reaction, a ring-opening reaction, or a cross-metathesisreaction.
 35. A method as in claim 13, wherein the catalyst has thestructure,

wherein M is Mo or W; R¹ is alkyl, heteroalkyl, aryl, or heteroaryl,optionally substituted; R² and R³ can be the same or different and arehydrogen, alkyl, heteroalkyl, aryl, or heteroaryl, optionallysubstituted; R⁶ and R⁷ can be the same or different and are heteroalkylor heteroaryl, optionally substituted, or R⁶ and R⁷ are joined togetherto form a bidentate ligand with respect to M, optionally substituted;and wherein R⁶ and R⁷ each comprise at least one oxygen atom.
 36. Amethod as in claim 35, wherein M is Mo.
 37. A method as in claim 35,wherein R⁶ and R⁷ each coordinate M via an oxygen atom.
 38. A method asin claim 35, wherein R⁶ and R⁷ are joined together to form a biphenolateor binaptholate ligand.
 39. A method as in claim 35, wherein R⁶ and R⁷are joined together to form a chiral ligand.
 40. A method as in claim35, wherein M is a Mo and R⁶ and R⁷ are joined together to form achiral, bidentate ligand of at least 80% optical purity, the chiral,bidentate ligand having sufficient rigidity such that a reaction site isof sufficient shape specificity, defined in part by the chiral,bidentate ligand and a M=N—R¹ site, to cause a molecular substratehaving a plane of symmetry to react with a M=C center at the reactionsite, forming a product that has at least a 50% enantiomeric excess ofat least one enantiomer present in the mixture, the product being freeof a plane of symmetry.
 41. A method as in claim 40, wherein the chiral,bidentate ligand comprises two linked oxygen atoms such that a group ofatoms defining the shortest chemical bond pathway between the two oxygenatoms has at least four atoms.
 42. A method for forming and using acatalyst, comprising: providing a catalyst precursor comprising anorganometallic composition including a first nitrogen-containing ligandin a reaction vessel; replacing the first, nitrogen-containing ligandwith a second, oxygen-containing ligand thereby synthesizing thecatalyst, at a temperature of less than 100° C. and with a yield of atleast 50%, in the reaction vessel; and catalyzing a reaction in thereaction vessel with the catalyst, wherein the catalyst is present at aconcentration of less than 100 mM.
 43. A method as in claim 42, whereinthe first, nitrogen-containing ligand does not interfere with thereaction.
 44. A method as in claim 42, wherein the second,oxygen-containing ligand is a heteroaryl or heteroalkyl group comprisingat least one oxygen ring atom.
 45. A method as in claim 42, wherein thesecond, oxygen-containing ligand is a bidentate ligand.
 46. A method asin claim 42, wherein the second, oxygen-containing ligand is a chiralligand.
 47. A method as in claim 42, wherein the second,oxygen-containing ligand is attached to a surface via a covalent or anon-covalent bond.
 48. A method as in claim 42, wherein the replacingoccurs at a temperature of less than 100° C.
 49. A method as in claim42, wherein the replacing occurs at a temperature of less than 80° C.50. A method as in claim 42, wherein the replacing occurs at atemperature of less than 60° C.
 51. A method as in claim 42, wherein thereplacing occurs at a temperature of less than 40° C.
 52. A method as inclaim 42, wherein the replacing occurs at a temperature of less than 25°C.
 53. A method as in claim 42, wherein the replacing occurs with ayield of at least 50%.
 54. A method as in claim 42, wherein thereplacing occurs with a yield of at least 60%.
 55. A method as in claim42, wherein the replacing occurs with a yield of at least 70%.
 56. Amethod as in claim 42, wherein the replacing occurs with a yield of atleast 80%.
 57. A method as in claim 42, wherein the replacing occurswith a yield of at least 90%.
 58. A method as in claim 42, wherein thereplacing occurs with a yield of at least 95%.
 59. A method as in claim42, wherein the catalyst is present at a concentration of less than 50mM.
 60. A method as in claim 42, wherein the catalyst is present at aconcentration of less than 10 mM.
 61. A method as in claim 42, whereinthe reaction is a carbon-carbon bond forming reaction.
 62. A method asin claim 42, wherein the reaction is an olefin metathesis reaction. 63.A method as in claim 42, wherein the olefin metathesis reaction is aring-closing reaction, a ring-opening reaction, or a cross-metathesisreaction.
 64. A method as in claim 42, wherein the catalyst has thestructure,

wherein M is Mo or W; R¹ is alkyl, heteroalkyl, aryl, or heteroaryl,optionally substituted; R² and R³ can be the same or different and arehydrogen, alkyl, heteroalkyl, aryl, or heteroaryl, optionallysubstituted; R⁶ and R⁷ can be the same or different and are heteroalkylor heteroaryl, optionally substituted, or R⁶ and R⁷ are joined togetherto form a bidentate ligand with respect to M, optionally substituted;and wherein R⁶ and R⁷ each comprise at least one oxygen atom.
 65. Amethod as in claim 64, wherein M is Mo.
 66. A method as in claim 64,wherein R⁶ and R⁷ each coordinate M via an oxygen atom.
 67. A method asin claim 64, wherein R⁶ and R⁷ are joined together to form a biphenolateor binaptholate ligand.
 68. A method as in claim 64, wherein R⁶ and R⁷are joined together to form a chiral ligand.
 69. A method as in claim64, wherein M is a Mo and R⁶ and R⁷ are joined together to form achiral, bidentate ligand of at least 80% optical purity, the chiral,bidentate ligand having sufficient rigidity such that a reaction site isof sufficient shape specificity, defined in part by the chiral,bidentate ligand and a M=N—R¹ site, to cause a molecular substratehaving a plane of symmetry to react with a M=C center at the reactionsite, forming a product that has at least a 50% enantiomeric excess ofat least one enantiomer present in the mixture, the product being freeof a plane of symmetry.
 70. A method as in claim 69, wherein the chiral,bidentate ligand comprises two linked oxygen atoms such that a group ofatoms defining the shortest chemical bond pathway between the two oxygenatoms has at least four atoms.